Glossary

Vessel gone dark

The moment every importer dreads: the dot on the map stops moving. Here's what it actually means — and how to tell routine from real trouble.

In one sentence

A vessel has "gone dark" when its AIS signal stops being received — most often because the ship sailed beyond terrestrial receiver range in the open ocean, not because anything happened to the ship or your cargo.

Why ships go dark

  • Open-ocean coverage gaps (the usual reason). Terrestrial AIS receivers reach roughly 40–50 nautical miles offshore. A transpacific crossing spends days outside that range, heard only by satellites — if your tracker doesn't buy satellite data, the vessel simply vanishes from its view.
  • Signal congestion. In crowded anchorages, AIS messages collide and some fixes are lost.
  • Transponder off. Rare in container shipping; legitimate in specific security zones, and a compliance problem anywhere else.

Why it matters for your ETA

The danger isn't the blackout itself — it's what your tracking tool does during it. Many platforms keep projecting the ETA forward and keep the dot marching confidently across the map, as if nothing changed. That's a stale estimate posing as a live one. If the vessel diverted, slowed for weather, or made an unplanned port call while dark, you find out days later — after your delivery promises were made on fiction.

What an honest tracker does instead

Three things: say plainly that the signal is gone, freeze the projection rather than extrapolating blind, and offer a way to actually re-acquire the ship — a satellite fix — with the cost stated up front. When the vessel reappears on terrestrial AIS, the track resumes with measured data, and the gap is visible in the history instead of painted over.

How Calibrate Freight handles gone-dark vessels

When a tracked ship stops reporting, Calibrate Freight raises a gone-dark exception, freezes the projected ETA and labels it frozen — never a stale dot posing as live. The watchkeeper agent can buy a satellite fix to re-acquire the vessel mid-ocean, and when it does, the action lands on a receipt: what it saw, what it did, how confident it was, and what the fix cost. When the ship reappears, the exception auto-resolves — with a receipt for that, too.

FAQ

Should I worry when my ship goes dark mid-ocean?
Usually not. Mid-ocean blackouts on terrestrial-only tracking are expected physics: no shore receiver can hear a ship a thousand miles out. Worry is warranted when a vessel goes dark near shore and stays dark, or when reappearance shows a big deviation from the planned track — both are reasons a tracker should raise an exception instead of staying silent.
How long do coverage gaps last?
On a transpacific run, terrestrial silence commonly lasts several days at a stretch, depending on route and receiver geography. Satellite AIS closes the gap on demand — that's exactly the moment a metered satellite fix earns its fee.
What happens to the ETA while a vessel is dark?
In Calibrate Freight, the projection freezes and is labeled frozen — the honest answer is "we can't measure right now," not a confident guess. Platforms that keep extrapolating through a blackout are showing you an assumption dressed up as data.

Related terms

AISThe radio broadcast every tracker is built on — how it works, and where its coverage gaps come from. TransshipmentYour box quietly changes ships at a hub port — and the vessel you're watching arrives without it. RolloverBooked on one sailing, loaded on a later one — why it happens and how to catch it before the ETA lies to you. Demurrage & detentionThe per-day charges that turn a late pickup into a four-figure invoice — and how the free-time clocks actually run.
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